The present invention relates to an adsorbent comprising a densified carbon black, and a process for adsorbing a gas with such an adsorbent.
The adsorption of gases is an important component of many industrial processes. The extent of adsorption is dependent on the ability of the adsorbent to contain the gas. The effectiveness of an adsorbent may be judged from several criteria, depending on the application. The adsorption capacity of the adsorbent may be expressed in terms of the adsorption per unit mass of the adsorbent, or in terms of the adsorption capacity per unit volume of the adsorbent. For some applications, such as the adsorptive storage of natural gas, space is a constraint, and so the adsorption capacity per unit volume of the adsorbent is the criterion for measuring its effectiveness. Thus, a good adsorbent should have a high adsorption capacity both on a unit mass basis, as well as on a unit volume basis. The adsorption capacity per unit volume of adsorbent is dependent on the adsorption capacity per unit mass, as well as the bulk density of the adsorbent material. Thus, increasing the bulk density of the adsorbent will cause an increase in adsorption capacity per unit volume of the adsorbent.
A number of carbon adsorbents have been investigated in the past. For example, Mullhaupt, et al., "Carbon Adsorbents For Natural Gas Storage", International Carbon Conference, Jun. 21-26, 1992, discloses the use of active carbon as a methane adsorbent, as well as the use of certain carbon blacks as methane adsorbents.
U.S. Pat. No. 4,999,330 to Bose, et al., describes a densified carbonaceous material for use as a methane adsorbent. As disclosed in this patent, while there is an increase in the density of the adsorbent of from 50% to 200%, the corresponding increase in the adsorption capacity per unit volume of the adsorbent ranges from about 20% to about 100%.
It is, therefore, an object of the invention to provide a densified carbon black that exhibits an adsorption capacity per unit volume superior to that shown by undensified carbon blacks.
It is a further object of the invention to provide a process for using such a densified carbon black as an adsorbent for gases.